Battery module, battery pack, and system comprising a battery module

ABSTRACT

The present invention relates to a battery pack for battery powered lighting systems comprising: —an outer wall surrounding the battery module made of a thermally insulating material, —a battery holder disposed within the outer wall comprising a plurality of battery receptacles in which batteries fit, and made of a thermally conductive material, and—a wireless power exchanger, comprising a wireless power tube coupled to the battery holder and disposed in the central opening, the wireless power tube being arranged for exchanging energy wirelessly with a wireless power stick that can be inserted into the wireless tube.

FIELD OF THE INVENTION

The present invention relates to a battery pack and more specifically to battery for battery powered lighting systems. This invention is, for example, relevant for battery packs for solar powered systems comprising a battery pack, for example such as solar powered off-grid street lighting.

BACKGROUND OF THE INVENTION

Today, more and more grid connected street lighting is replaced by solar powered off-grid street lighting, also referred to as solar powered OSL. Present solar powered street poles use batteries to store the energy harvested during the day for use in the night. The most frequently used battery type for this purposes is a lead battery (i.e. Pb battery), because of its relatively low cost. Present Pb batteries have a relative short life of 2 to 3 years. This is mainly caused by the solar application: when a Pb battery would be recharged immediately after discharge, and with the correct charging profile, it may enjoy life of up to 5 years. But the solar application does not always produce enough current for a complete recharge, especially in the winter where the Pb battery is run in a partially charged condition (i.e. partial State Of Charge). The result is that Pb is typically short lived at 2 to 3 years which is not deemed sufficient. Battery lifetime is considered a main differentiator.

Alternatively, lithium batteries may be used which have much longer life, with claims of 20 years under optimal conditions. But also for Li-Ion, the outdoor solar charging conditions limit life, this time caused by the temperatures under operation. The batteries' performance under cold conditions is a fraction of the performance under warmer test conditions of typically 25° C. This is caused by the Arrhenius factor, which describes the limited chemical kinetics at lower temperatures. In addition, when using Lead acid batteries, at temperatures slightly below zero the electrolyte will freeze up. In both cases, the mitigation is to over dimension the battery, so it can still release enough power.

Some battery technologies will degrade when charged at subzero temperatures. An example is the above mentioned Li-Ion technology, which will suffer from Lithium plating under such conditions when it is charged with a high current, resulting in a very strong reduction in life. Mitigation against Lithium plating may be to bury the battery under ground below the frost layer, at e.g. 1 m. But again, this will add cost for ground works and temperature may still be low enough to limit life when the battery is operated below the thermal comfort zone, although not as drastically with lithium plating. Another mitigation is to limit the charge current when the battery is cold, but since the charge duration is limited to the daytime and it is almost impossible to plan charging interruptions due to clouds and shadows, the battery may not be fully charged.

SUMMARY OF THE INVENTION

It is an object of the invention to propose a battery module which alleviates the above mentioned problems.

It is another object of the invention to propose a battery module having a higher lifetime.

It is another object of the invention to propose a battery module which may operate efficiently despite difficult conditions.

Still another object of the invention is to propose a battery module that is simple and cheap to manufacture.

To this end, the present invention relates to a battery module comprising an outer wall surrounding the battery module made of a thermally insulating material, a battery holder disposed within the outer wall comprising a plurality of battery receptacles in which batteries fit, and made of a thermally conductive material.

By the combination of a thermally conductive material inside and the thermally insulating material on the outer wall, the battery temperature can be more easily maintained in a comfort range. Thus, the negative effects of temperature on the lifetime and performance of the battery can be prevented. In particular, in case of outdoor operation, like for example in a solar power outdoor luminaire, like an off-grid street lighting, the internal temperature of the battery does not drop easily to sub-zero temperatures, not does it overheat to very high temperatures.

In accordance with an embodiment of the invention, the battery module may comprise a central opening, and a heat source may be installed in the central opening of the battery module. Thus, the heat source can maintain the temperature inside a comfort range. The thermally conductive material ensures that the heat is easily spread within the battery module, so that all the batteries of the module are approximately at the same temperature. The outer wall maintains the produced heat inside the battery module. The heat source may be a resistance or a cable traversed by an electric current.

In one particular example of this embodiment, the heat source is formed by a wireless power exchanger, comprising a wireless power tube coupled to the battery holder and disposed in the central opening, the wireless power tube being arranged for exchanging energy wirelessly with a wireless power stick that can be inserted into the wireless tube. The losses during the power transfer at the wireless exchanger are used to heat the battery module. Thus, during the charge or the discharge of the battery module, heat is produced which is spread by the thermally conductive battery holder. Another advantage of the use of a wireless power exchanger is that no wirings or connections are needed. Thus, the installation is safer and easier and the battery modules having no apparent connection terminal are less prone to be stolen or vandalized.

In this variant, the wireless power tube may comprise a first winding for receiving power from the wireless power stick and a second winding for transmitting power to the wireless power stick. Thus, the coupling may be adapted so that the voltage and current for charge and discharge of the batteries are adapted to each situation. However, it is also possible that the wireless power tube may comprise a single winding for receiving power from the wireless power stick and for transmitting power to the wireless power stick. The adaption of voltage and current may be done in the battery module or at an external unit. This version of the battery module is thus simpler and less expensive to manufacture.

In another embodiment of the invention, which may be combined with the previous embodiment, the battery module comprises a temperature sensor for sensing the temperature of the batteries in the battery holder. Thanks to this sensor, the internal temperature of the battery module can be monitored, so that actions may be taken to avoid that the battery life is endangered, like e.g. stop using the battery until the temperature is back in the comfort zone.

In particular, in a variant of this embodiment, the battery module further comprises a controller arranged for monitoring the temperature sensed by the temperature sensor and for causing the heat source to be activated based on the sensed temperature. Thus, when the temperature is decreasing too much, the controller of the battery can either on its own, or by means of an external unit, trigger the heating of the battery module by the heat source. For example, in case the heat source is a wireless power exchanger, the controller can trigger a power transfer from the batteries through the wireless power exchanger. The heat losses caused by this discharge are reheating the battery module which thus avoids getting out of a comfort zone of the batteries.

In a further example of this variant of the invention, the controller is further arranged to signal to an external unit at least one parameter value, the parameter value being one of the group comprising: the sensed temperature, a state of charge of the batteries, a failure of at least one battery. The signalling of the sensed temperature can be the trigger of the power transfer through the wireless power exchanger mentioned above. Indeed, the charge and discharge of the battery module may be controlled by an external unit which decides to discharge the battery module based on the signalled sensed temperature value and/or on the state of charge of the batteries. A failure of at least one battery may trigger the intervention of a technician for the replacement of the failing battery.

For example, the controller may be arranged to signal to the external unit the parameter value via the wireless power exchanger. It is possible to, for example, modulate a signal into the frequency of the wireless power transfer or embed the signal information via other means so that the signal can be retrieved from at the external unit. Thus, no wirings or connections are needed to connect the battery module to the rest of a system. This enables an easier installation of the battery module into a system.

In a particular variant of the first embodiment, the battery module is of cylindrical shape or of a prism shape, centered around a revolution axis, wherein the central opening is centered around the revolution axis. This particular shape and disposition ensures a homogeneous and efficient spread of the heat in the battery holder. Moreover, this shape is particularly well adapted to the installation in poles, like lighting poles. Other shapes could be contemplated like for example a discus shape (i.e. a flat cylinder) which may be installed on top of the pole.

In the meaning of the patent application, a prism is a polyhedron with an n-sided polygonal base, a translated copy (not in the same plane as the first), and n other faces (necessarily all parallelograms) joining corresponding sides of the two bases. Moreover, the term “cylinder” should be understood as any volume formed by two curve sections (e.g. circle, ellipse) which are linked by a joining surface. A rod shape cylinder is the specific case when the sections are two identical circles.

To keep the battery as compact as possible, it is proposed in an example of the above variant, that the battery controller of the battery module extends radially from the revolution axis between the central opening and the outer wall, occupying an arc segment of a base section of the battery holder, the plurality of battery receptacles being spread in a remaining arc segment of the base section of the battery holder so that a thermal gradient in the battery holder is optimized.

In another embodiment of the invention which can be combined with the previous embodiments, the battery module is shaped so that a plurality of battery modules can be stacked on top of each other around a wireless power stick. Thus, the battery modules can be used in a system either alone or in a compact battery pack. This provides a flexibility of use depending on the needs of the installer for each situation, while keeping the solution as compact as possible. To this end, the shape may comprise a groove on one side corresponding to a shoulder on the other side.

In accordance with another aspect of the invention, it is proposed a battery pack comprising one or more battery module in accordance with the first aspect of the invention.

In an embodiment of this aspect of the invention, the battery pack comprises a power channel controller which is adapted to control the energy transfer with the battery modules based on at least one of the following parameters: internal temperature of the respective battery modules, input voltage from an energy harvester, input current from an energy harvester, position of the respective battery module in the battery pack, state of charge of the respective battery module.

Thus, the power channel controller is able to decide how to charge individually the modules of the battery pack depending of the needs. In an example of the invention, the battery modules being stacked up, it is interesting to charge up the bottom battery module in priority, so that the whole stack of the battery modules can benefit of the heat caused in the wireless power exchanger at its bottommost part.

In a further variant of this embodiment, the power channel controller is adapted to control the energy transfer to maintain an optimal efficiency of the energy transfer by adjusting at least one of the following parameters: voltage, current, frequency. Thus, despite the fluctuations of power level harvested at the solar panel for example, due to changing illumination conditions, the power channel controller can maintain the efficiency level during the charge or discharge of the battery modules, by adjusting the frequency of the current in the windings, the voltage and/or the current. For example during the charge, it is preferable to maintain the voltage at the nominal charging voltage, so the power channel controller will adjust the current and the frequency to maintain the coupling and the power transfer at an optimal or close to optimal point.

In another embodiment, the power channel controller is adapted to control the energy transfer to an operating point having a selected efficiency based on an amount of heat to be injected in the battery module. Indeed, depending on the needs for heat into the battery, for example in cold conditions, a slightly less optimal operating point may be chosen, to ensure that the power transfer at the wireless power exchanger is producing enough electrical losses. These electrical losses are, by Joule effect, converted into heat which ensures that the battery is maintained in a thermal comfort zone.

In an embodiment of this aspect of the invention, the plurality of battery modules comprise each a central opening, the battery module further comprising a wireless power exchanger formed by a plurality of wireless power tubes being each respectively coupled to the battery holder of each battery module of the plurality of battery modules and disposed in their respective central opening, and a wireless power stick inserted into the wireless power tubes of the battery modules and arranged for exchanging energy wirelessly with the plurality of wireless power tubes.

In accordance with still another aspect of the invention, it is proposed a lighting system comprising, an illumination unit, a battery module in accordance with the first aspect of the invention or battery pack of the second aspect of the invention, for supplying the illumination unit in power, an energy source for supplying the battery module or the battery pack in power.

In accordance with this aspect of the invention, the energy source may be an energy harvester like a solar panel, or a windmill harvester. It is also possible that the power source is the grid, the battery being used as a backup in case of power shortage. Such power shortage may occur daily in some developing countries. Thanks to the benefits of the battery modules, such an illumination system can be used even in difficult outdoor conditions, like in cold winter with less impact of the reliability of the battery.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which

FIG. 1 shows an example of a battery powered lighting system being a solar powered light pole;

FIGS. 2A, 2B and 2C schematically show an embodiment of a battery module;

FIG. 3 schematically shows a cross section view of an embodiment of the battery module;

FIG. 4A is the representation of wirings on the bottom and top parts in accordance with an example of the invention and FIG. 4B is a representation of the corresponding electric circuit formed by the battery module in a first embodiment.

FIG. 5A is the representation of wirings on the bottom and top parts in accordance with an example of the invention and FIG. 5B is a representation of the corresponding electric circuit formed by the battery module in a second embodiment.

FIG. 6 schematically shows a top cross view of another embodiment of the battery module with a wireless power stick installed;

FIG. 7 schematically shows side cross section view of a battery pack with a wireless power stick installed.

FIG. 8 is a block diagram representing a lighting pole in accordance with an embodiment of the invention.

FIG. 9 is a side cross section of a battery module in accordance with an embodiment of the invention.

FIG. 10 is block diagram representing a lighting pole in accordance with an embodiment of the invention.

FIG. 11 is a representation of a luminaire installed in a rooftop in accordance with an embodiment of the invention.

FIG. 12A and FIG. 12B is representing the steps of installation a luminaire in accordance with variants of an embodiment of the invention.

FIG. 13 is a representation of a luminaire installed in a rooftop in accordance with another embodiment of the invention.

FIG. 14 is representing the steps of installation a luminaire in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an example of a battery powered lighting system being a solar powered light pole 10. The light pole comprises an illumination unit 11 supported by a pole 12 having a widening 13 near the ground (not shown). The system in this example also comprises a Photovoltaic (PV) panel 14 arranged to generate electrical power using sun light. Inside the widening 13 of the pole 12 a battery pack (not shown in FIG. 1) may be arranged to store electrical energy received from the PV panel 14. In other examples, other types of energy may be harvest by means of a different harvester, like for example a windmill. If the battery pack is charged, it can provide electrical power to the illumination unit 11. The illumination unit 11 may comprise LEDs or any other lighting elements using electricity. It should be clear that the battery pack is stored inside the pole 12 but that it can be stored anywhere in the pole 12, preferably above ground level to avoid unwanted temperature gradients.

The battery pack inside the pole 12 may comprise one or more battery modules. FIGS. 2A, 2B and 2C schematically show an embodiment of such a battery module. In this embodiment, as shown on FIG. 2A, a battery module 20 comprises a substantially cylindrical housing comprising an outer wall 21 and a bottom (not shown) and a cover 22. At a central part of the module 20 an opening 23 is arranged surrounded by a tube shape pipe 24 which extends upwards. FIG. 2B shows the battery module 20 of FIG. 2A but with the cover 22 removed, and FIG. 2C shows the battery module 20 of FIG. 2A but with the cover 22 and the wall 21 removed. As can be seen from FIG. 2C, the module 20 comprises a cylinder shaped inner body 26 (serving as a battery holder) having a plurality of holes or receptacles 27 for holding the battery cells (i.e. the batteries). In this embodiment, the battery cells are arranged in parallel and co-axial with the central pipe 23. The module 20 shown is especially suitable for powering lighting systems having cylindrical shaped poles. It should be understood that other shapes for the modules are possible, and this may depend on the application.

FIG. 3 schematically shows a cross section of an embodiment of the battery modules 20 placed inside the pole 12. As can be seen the inner body 26 comprises a plurality of holes 27 for placing the batteries.

At an inner part of the module an electronic module 31 is arranged which may comprise a first temperature sensor 32. The first sensor 32 is arranged to measure the temperature of the batteries. The electronic module 31 operates as a controller of the battery module 20 to measure the temperature sensed by the first sensor 32 and may also measure the state of charge of the battery. The electronic module may also detect when a battery cell is failing. This electronic module extends in this example radially from the center for a very compact module (no further thickness needed on top of the battery cells. Because of this inhomogeneity in the inner body 26, the battery receptacles 27 have been places asymmetrically for an optimal spread of the heat in the inner body, obtained for example by simulation. It can be seen that the battery receptacles 27 are less spaced apart in the vicinity of the electronic module for this reason.

The inner body 26 is preferably made of a thermal conductive material, such as for example stanyl or other highly heat conductive material, so that the temperature of the batteries across the module will not deviate too much, and the temperature measured by sensor 32 will reflect the temperature of all the batteries.

The outer wall 21 of the module is preferably made of a thermally insulating material, such as for example aerogel or polystyrene so that the batteries are isolated from their surroundings, and less heat will be lost from the inside. Around the hole 23 an additional isolating tube 33 may be present to isolate the batteries towards the central axis. It is to be noted that the outer wall, in particular its thickness may be dimensioned in accordance to the climatic conditions that the battery module will face during operation. Therefore, although the inner body or battery holder 26 may be of standard shape and size, the battery module may still be tailored to the conditions by adjusting the dimensions of the outer wall 21 for example.

The battery module 20 also comprises a groove 34 for cable guidance inside the pole 12. In the example of FIG. 3, a second temperature sensor 35 is arranged at the outside of the pole 12. The second sensor will measure the outside temperature, also referred to as ambient temperature.

It is to be noted that the battery module may further comprise a housing not shown, for example a water tight housing or a rigid housing, for protecting the battery module from shocks, water, dust from the environment. This housing may for example be made of molded plastic material offering enough shock absorbance, and protection for the battery module. It may also be designed to pass some conformance, safety or approbation tests depending on the conditions of use of the battery.

In the exemplary battery module 20, 24 battery cells can be fitted. Again, some flexibility is offered with respect to the operating voltage and current, depending on the connection chosen. In accordance with this example, the battery module 20 comprises a base section having an upper surface having conductive leads for connecting the battery modules one to another; and a top section having a lower surface having conductive leads for connecting the battery modules one to another. In the example of FIG. 4A, it is shown an example of the conductive straps or wirings to be used to interconnect the battery cells 41. On this drawing, plain connections 42 represent the conductive straps used on one side, for example on the lower surface of the top cover to connect the upper end of the battery cells 41. Dashed connections 43 represent the conductive straps used on the other side, for example on the upper surface of the bottom part of the battery module to connect the lower end of the battery cells 41. The conductive straps may be for example made of nickel plates stuck on the bottom part and on the cover of the battery module. The battery cells 41 are then disposed in the battery holder appropriately to respect their polarity.

The equivalent electronic scheme is represented by FIG. 4B, which shows that the module is provided with a 2 parallel branches, comprising 12 battery cells in series.

A variant of the above example of the invention is represented on FIG. 5A and FIG. 5B. In this case, the module is provided so that the 24 battery cells are connected with 3 parallel branches, comprising each 8 battery cells in series. Obviously, these wiring schemes are illustrative and many alternative solutions may be chosen to connect the battery cells.

In accordance with an embodiment of the invention, the central opening is designed to be modular, and for example a heat source may be placed in the central opening 23, so that an acceptable temperature is maintained at the battery cells. This heat source is particularly suitable in case the battery module is to be used in very cold conditions.

In accordance with a variant of this embodiment, the heat source may be a wireless power exchanger, as represented on FIG. 6. On this Figure is represented a battery module with a structure similar as the embodiment of FIG. 3. However, in addition with the previously explained battery module, a wireless power exchanger is located in the central opening 23. This wireless power exchanger is formed by a wireless power tube 61, which comprises an internal winding 610 and a shielding 612, and a wireless power stick 63 inserted into the wireless power tube 61. The wireless power stick 63 comprises an internal winding 631, which corresponds to the internal winding 610. The wireless power stick 63 may also include a shielding (not shown), disposed inside the wireless power stick to prevent any unwanted coupling with internal wirings for example. The respective diameters of the wireless power tube 61 and the wireless power stick 63 are such that a minimal air gap 62 may be formed in between.

The shielding 612 of the wireless power tube 61 prevents any degradation of the coupling at the wireless power exchanger due to an unwanted interaction with the metal cans of the battery cells. In the battery module of FIG. 6, the wireless power exchanger comprises only one pair windings 610 and 631, so only one possible coupling for transferring power into the battery and extracting power from the battery. It is possible to implement the wireless power charging and discharging with one pair of coils, for example by implementing a wireless-power channel-controller which has an optimization controller and algorithm to adapt the power transfer efficiency to fluctuations in current and voltage caused by variations in sun power or variations in the discharge load, for example caused by cold temperatures or by dimmed light levels.

Alternatively, some implementations may require two pairs of windings, one for receiving power at the battery module, another for transmitting power from the battery module. It is also possible to have a wireless power channel controller as introduced briefly above in combination with these two pairs of windings per battery module, for example to cope with the fluctuations of the harvested energy from a solar panel or a windmill or fluctuations in the discharge load. In this example, each battery module uses one coil for Transmission/Tx and another coil for Receiving/Rx. Thus, the system above uses a separate coil pair for charging and another separate pair for discharging, resulting in two separate wireless power channels. This is an optimization of the system disclosed earlier since in the exemplary solar powered lighting application the charging regime requires other currents than the discharging regime. Such a system may yield better coupling and higher efficiencies.

With reference to FIG. 7, it is represented a cross section of a battery pack comprising two battery modules 20-1 and 20-n stacked one on top of another and comprising a set of battery cells 271 and 27 n respectively. The battery pack comprises a wireless power exchanger formed by the wireless power tubes of the battery modules 20-1 and 20-n and a single wireless power stick 63. Each wireless power tube 611-61 n comprises a pair of coils (or windings) 731-73 n and 741 to 74 n. In each battery module, one winding 731-73 n is used when charging the battery cells, the other 741-74 n being used for the discharge of the battery cells. Similarly, the wireless power stick 63 transmits power to the respective wireless tubes with the windings 711-71 n facing each a corresponding winding 731-73 n of the wireless stick (for the charging of the battery cells) and receives the power at the windings 721-72 n facing each a corresponding winding 741-74 n (during the discharge of the battery cells).

A power channel controller 75 is connected to each wireless power tube windings 711-71 n, 721-72 n by means of a set of wires 76, and controls the transfer of power into or from the battery modules. The power channel controller may also adjust for example the voltage, the frequency or the current to make sure that the efficiency of the each corresponding coupling formed at each couple of windings (tube-stick) is always optimal in terms of efficiency. However, it may also be useful, in case the internal temperature is dropping quickly, or the temperature outside is very low, to degrade the efficiency of one or more of the coupling, thus generating more heat.

FIG. 8 represents schematically of a solar powered luminaire including the battery pack of the embodiment described in reference of FIG. 7. As can be shown on FIG. 8, during a charging phase, the solar panel 14 generates some power when the illumination is sufficient. This power is a Direct Current (DC) which is brought to the power channel controller 75, which can then adjust the power transferred through the wirings 76 to make sure that the coupling at the wireless tube 63 is optimal. An alternating current is applied on windings 711 and/or 71 n selectively to transfer power to the battery modules 20-1 and/or 20-n via their respective windings 731-73 n. The alternating current received at the windings of the wireless tubes 611-61 n is then converted into a DC current for charging the battery cells 271-27 n. The electronic modules 311-31 n adapt the received power if an adjustment of the voltage is required for example. Moreover, the electronic modules 311-31 n monitors parameters like the state of charge of the battery cells 271-27 n or their internal temperature measured by the temperature sensor. Then, during a discharge phase, the electronic modules 311-31 n output a current from the battery cells to the windings 741-74 n of the wireless power tubes 611-61 n. This current has been prior turned into an alternative current with the adequate frequency for the wireless power exchanger. Thanks to the coupling of the wireless power exchanger, the power is received at the wireless stick windings 721-72 n. The wireless power channel controller 75 controls and adjusts the transferred wireless power by adapting the load at the wireless stick 63. The output power is then applied to the load, here a luminaire. The wireless power channel controller may choose to use any combination of battery modules 611 to 61 n in any sequence to maximize the electrical efficiency and thermal efficiency as required.

It is to be noted that in the above example, only 2 battery modules were shown for the sake of clarity. However, the number of the battery modules that can be stacked up in accordance with these embodiments may be more than 2.

As indicated above, the battery module can be stacked on top of each other. FIG. 9 illustrates an example of a stackable battery module. In this battery module, the bottom part forming an outer wall 21 comprises a shoulder forming a tubular protrusion 91. This shoulder 91 is dimensioned to correspond to a shoulder 92, such that the two tubular protrusions 91 and 92 can penetrate one another. Similarly, the wireless power tube 61 comprises a protrusion 94 on its upper part which corresponds to a recess 93 of its lower part. This permits to align the wireless tubes in an accurate manner, such that a wireless power stick can be inserted into the tubes, with a very small air gap.

Indeed, wireless power field coupling is influenced in the X and Y and Z axis and is optimal when the coils are well aligned. The X and Y axis shall be optimized by minimal air spacing between stick and tube. The Z axis (shown on FIG. 7) shall be optimized by the notches 93 and 94 that will assure that the transmitter coil and receiver coil are perfectly aligned.

One of the advantages of the battery module shown in the previous embodiments is that dimensioning the battery pack is very simple. A separate tool estimates the amount of energy (charge) that will be required for the given installation (depending on the load, the power source, the frequency of the charging opportunities, the risk that a charging opportunity is missed) to determine the size of the battery pack and the number of battery rings that will be required. A battery stick of correct size is selected and inserted into the hole of every battery module until all battery rings are stacked up the wireless power stick. No wiring will be required and this step completed the physical installation.

Alternatively, as indicated earlier, it is also possible to implement the wireless power charging and discharging with one pair of coils, by implementing a wireless-power channel-controller which has an optimization controller and algorithm to adapt the power transfer efficiency to fluctuations in current and voltage caused by variations in the power source, for example the sun power or fluctuations in the load which may be caused by for example dimming.

A conservative computation was made for the field efficiency based on a specific example architecture to demonstrate that high field efficiencies can be achieved. It shall be appreciated that the mechanisms set forth will also work for other architectures with other resultant voltage and currents.

The resultant voltages and currents of these options are listed in the Table below.

The wireless power bus is assumed to have 15% losses. These losses are based on and additional to the values from the Table and will be injected as heat into the battery ring via the wireless power core. It is important to match the battery pack voltage with the voltage used in the wireless power system to achieve high field efficiencies. The application is analysed for the typical voltages and currents under all possible battery architectures of X cell serial and Y cells parallel as listed in the Table below. In this case the 24 positions for battery cells as shown in FIGS. 4A and 5A can support for example an 8S3P battery architecture or a 12S2P architecture.

24 cells 8S3P 12S2P architecture architecture V (Vdc) I (A) V (Vdc) I (A) Charge use case 1: average current 33.6 0.450 50.4 0.300 from sun Charge Use case 2: solar 33.6 1.450 50.4 0.970 charger maximum 300 W = 12.5 A@24 V Charge Use case 3: configured 33.6 0.780 50.4 0.520 solar charger limit 163 W = 7.0 A@24 V Dis-charge Use Case 1: 25 W LED 29.6 0.121 44.4 0.080 light (Note1) Dis-charge Use Case 1: 50 W LED 29.6 0.241 44.4 0.161 light (Note1) (Note1): Discharge Voltage @ start of discharge. During discharge voltage decreases & current increases.

In this lighting application the voltage will not remain stable, nor the current.

-   -   During charging the voltage may change due to fluctuations in         temperature of the PhotoVoltaics and the current may change due         to fluctuations of the present irradiance.     -   During discharging of the battery the voltage will decrease and         the current increases. Temperature may influence voltage levels         and capability to sustain the power. In addition dimming will         influence the power level during discharge as well.

The resultant wireless power core needs to be optimized to support flexibility in voltage and current. As an example of the expected performance of the wireless power channel, the charge Use Case #3 will now be analyzed.

The chosen coil to coil coupling is conservative at 50% in this example.

1. The system will charge 26.2 W (33.6 VDC*0.78 A) into the battery. The battery side of the wireless power core is the receiving coil or the secondary load. The power channel controller, based on stored data regarding the efficiency of the coupling on the operating point will thus search for an optimal operating point based for example on current and/or voltage and/or frequency to be applied at the primary side.

2. based on stored helper graphs, the power channel controller will find out that 30.5 W is required as primary power; i.e. the power that the system must generate so that the desired 26.2 W is received in the battery. At this point the wireless power transmitter in the wireless power stick needs to operate at 9.68V and 3.15 Å. In this example, stored helper graphs are used, however, alternatives are possible. For example, the power receiver (i.e. the battery module) may control itself to the desired operating point (in the example above 33.6V/0.78 Å), for instance by sending “control error” information (requests for less/more power) to the power transmitter (i.e. the power channel controller). The power transmitter will react by adapting its frequency or voltage (where the voltage can also be adapted by changing the duty cycle of the power signal).

In another implementation, the controller is selecting an operating point from a set of preconfigured operating points based on the current need for efficiency, for example if there is a large need of heat, a low efficiency point may be selected. On the contrary, when only power conversion is required, for example in warmer conditions, a high efficiency point may be selected. A trade off is to be considered to balance between an efficient power transfer and the amount of heat injected into the battery module. This means that, as seen above, in certain circumstances the system will not attempt to achieve optimal power transfer efficiency, but will opt for slightly less efficient working points because the system needs some extra heat, to keep the batteries in the thermal comfort zone.

The difference between input and output is electrical loss, which is injected into the battery module as heat.

Note: as explained in the system overview, the wireless-power channel-controller shall be able to constantly adapt to the variations in current and voltage as caused by the fluctuation in sun power. The wireless-power channel-controller shall attempt to achieve the most optimal power transfer efficiency, but may deviate from the most optimal points to generate enough heat through electrical losses, as required and possible by the system.

It is to be noted that the power transfer efficiency can be much higher than the previous example by improving coil to coil coupling by for example careful optimizations of placement and format of the coils. Another example with a higher field coupling of 70% and resultant power transfer efficiency better than 95% is also possible. As a result, such a system has hardly any electrical losses but also very minimal heat injection. The system can be designed on working points where it can a.) generate enough heat but b.) also avoid large additional energy requirements.

It shall be appreciated that the discharging use case shall work in similar ways, be it either as a separate coil pair in a system with separate coil pairs for charge and discharge or in a system where there is one coil pair for charge and discharge.

One of the advantages of the battery in accordance with the embodiments of this invention is that such battery can be easily produced to a large scale.

Indeed, a fully automated manufacturing process can be designed for example with a pick and place robot.

-   -   The wireless power core component is inserted into the thermal         conductor ring component. Since the wireless power core is         another implementation of the core component with the same         physical outer dimensions, the placement is identical with as         additional extra the wiring from the wireless power coils to the         battery management electronics. These wires are soldered into         place prior to placement.     -   Rounded corners of the battery holes will facilitate easy         placement of the battery cells.     -   After placement of the battery cells in the thermal conductor         the robot may put connector disc containing interconnector leads         as shown on FIG. 4A or 5A on top of the battery and welds the         connectors between the cells.     -   After welding the top battery cell connections the robot may         turn the pack around and put another connector disc on top         (which is actually the bottom of the thermal conductor ring. The         bottom connections between the cells are also welded in place.     -   Battery plus and minus will be interconnected from the cells to         the battery electronics.     -   After electrical test is completed the battery conductor with         battery cells, battery management electronics and wireless power         core will be placed into a box for structural rigidity and         safety which is completely sealed by e.g. ultrasonic welding.     -   The isolating outer wall will be placed over the safety box (or         may be part of the safety box).

The assembled battery ring is now completed for final test with a wireless power stick connected to a wireless power channel controller which will run a simulated test. The test results will be read via the command channel which is modulated over the wireless power field and stored for analysis.

In the battery module of the previous embodiments, it is possible to use standard battery cells, for example Li-Ion cells 18650.

Although the battery cells are standard, it is possible to adjust the some characteristic of the battery modules to adapt to the installation conditions. In an example, it is possible to vary the thickness of the insulating outer wall depending on how low the temperatures can be. The colder the conditions, the thicker the insulating wall. Moreover, it is possible to dimension the wireless power exchanger to be less efficient, for example by increasing the air gap between the wireless power tube and the wireless power core. If the efficiency of the wireless power exchanger is lower, it creates more heat during operation, which thus enables to maintain more easily the internal temperature of the battery cells. A too efficient wireless power exchanger may not generate enough heat for this purpose if the conditions are cold.

In order to adjust the efficiency of the wireless power exchanger to the installation conditions, it is possible to design a single diameter for the wireless power tube and select one out of several diameters for the wireless power stick. The opposite is also possible, i.e. a single diameter for the wireless power stick and different diameters for the wireless power tube.

Eventually, as indicated earlier, it is possible to stack up a plurality of battery modules in a single battery pack depending on the needs of power in an implementation.

An alternative system architecture depicted on FIG. 10 can optimize overall system efficiency by replacing the DC cable from the top of the pole to the battery below with AC cabling. Indeed, in some cases, an illumination post can be quite high, like for example on highways, or on the taxi zone of an airport. An AC cable over many meters can be thinner and cheaper, have less resistance losses than a DC cable. The additional AC/DC conversion is operated by a DC/AC converter 1001 and an AC/DC converter 1002. Thus, the power can be transmitted over AC power cables from the power source 14 to the power channel controller 75 and between the power channel 75 and the illumination unit. Such conversions can be implemented in a very efficient way.

In another embodiment, it is proposed to use the battery pack of the invention for rooftop installations instead of a pole.

Indeed, when installing lighting, a skilled electrician normally needs to install a high voltage AC power network to attach lights thereto. Typically a 230 VAC (Europe) or 110 AC (US) is installed in a building. In other countries other voltages may apply. Alternatively, the power could be drawn from a Photo Voltaic installation, which is converting power to AC and inject it then into the high(er) voltage power grid of the building, but one still needs the higher voltage network where the lamps are connected thereto.

It is also common to install the power cables and wires comprising the high(er) voltage network to the ceiling, either by cable clips or pipes (which are e.g. carved and placed in walls or poured into concrete floors, or installed in a wooden floor or by entirely different means). There are many possibilities and regulations in different countries how to install a high(er) voltage network into a building, but that is not important for present invention.

The aim of this embodiment is to avoid installation of a high voltage network. The present embodiment utilizes uses an energy source that is harvested outside the building and delivered through the roof without any cable connections. The energy source includes for example a Photovoltaic module including Photovoltaic cells, or a wind mill, or any other energy harvester that can harvest energy from the environment.

Thus, the entire cost for the high voltage network is avoided. The associated installation costs for a high voltage network are also avoided. These costs can be large, as this may include a large portion of labour, for building the high voltage network: possible actions are e.g. for hacking and breaking into walls or pre installation before pouring concrete or drilling through floors. Some expensive supportive equipment is not required by the installation of this embodiment, such as for example scaffolding to reach out to a high ceiling, rental of bucket cars, etc. This lowers overall cost (i.e. Capex).

Moreover, higher voltages need to be handled with care and are not required anymore. Normally, high voltage installation requires a skilled electrician. Since there is no requirement for a high voltage network, its associated requirements for a skilled electrician and hence more expensive labour is not required.

As such, the present embodiment is also very suitable for use in countries with a lack of skilled labour as its installation is simple and safe.

In accordance with this embodiment, a device and its installation method are defined. In this embodiment, it is proposed to extend the battery pack comprising a wireless charger stick and at least one wireless battery, for example as described in the previous embodiments, with an electrical load, such as for example a light and/or a fan. The whole stick including the charger part and the lighting part, is installed through the roof. On the outside of the building, which means on top of the roof, the stick comprises an energy harvester, such as for example a Photovoltaic cell or panel or a windmill.

Therefore, in accordance with this embodiment, a wireless stick comprises:

-   -   a power exchange coil arranged for exchanging energy wirelessly         with a wireless power tube once inserted into the wireless tube.     -   an energy harvester adapted for harvesting energy from the         environment     -   a load powered by the energy harvested by the harvester and/or         the energy exchanged by the power exchange coil.

Indeed, the wireless stick comprises an energy harvester preferably at one end (e.g. the top end) and an electrical load to the other end (e.g. the bottom end). Thus, once installed through a rooftop or a wall, the harvester can harvest energy from the environment and the load can be used inside the building (for example a light for illuminating the building).

To install the wireless stick, an opening in an overhead protective structure (e.g. a rooftop) can be used, so that the energy harvester is on the top of said overhead protective structure to harvest energy from the outside environment. The bottom of the stick is positioned under the overhead protective structure where the electrical load is required to operate. An energy storage, like for example a wireless battery as described in the previous embodiments, can be installed around the stick and does not require any wiring or cabling, since the contacts between the energy harvester or energy source, the energy storage and the electrical load (e.g. lamp) can all be wireless. In another variant, only the connection with the energy storage is wireless, the other connections (to the load and to the energy harvester) can be done by wires integrated in the wireless power stick. This provides with a device and methods that simplifies installation and operation.

The method for installing a load included in this embodiment comprises the steps of

-   -   install a wireless power stick through an opening of a building,         so that a first end protrudes towards the outside of the         building and a second end protrudes towards the inside of the         building,     -   attaching a wireless battery to the wireless stick so that the         wireless power stick can exchange power with the wireless         battery,     -   connecting an energy harvester to the first end to the wireless         power stick,     -   connecting the load to the second end of the wireless power         stick.

The wireless stick can be secured from the inside, for example with the wireless battery shaped in a ring for energy storage. Importantly, there is no need for wiring or the actions associated to connecting wires and connectors. Said stick can harvest photovoltaic energy on top of the roof and provide lighting below the roof.

The device may start and stop lighting up the interior of the building if this is desired and/or required, and this is preferably automated by a sensor. One example is a luminance sensor that starts the lighting when ambient light levels fall under a specified, certain threshold and stop lighting when the ambient light level raises above another specified, certain threshold. The working of a sensor to start and stop light is mentioned to explain that the system will work without for example a lighting switch installed on e.g. a wall, which is typical for a high(er) voltage 230 VAC installation.

The present embodiment is explained in FIG. 11.

Elaborating on FIG. 11, the device is comprised of several parts. The present invention will offer a charger stick 110, which may be extended by a connector 101 to power an electrical load 102. This electrical load may be a plurality of lights 103. The stick 100 may be combined with a light guide 104 for guiding light from the outside towards the inside of the building. Thus, during daylight, some natural light can be guided towards the inside of the building, for example when the lights 103 are switched off. The charger stick 110 does contain a wireless charger channel comprised transmitter and receiver pair 124. Further to said wireless charger channel, the wireless power transmitter is located in the charger stick 100 and a receiver in the wireless power core 122. The wireless power core 122 is slid over the wireless power stick 100 and transmits power without the need to install any connecting wires in between. The wireless power core 122 is connected to energy storage 120 to store the power for direct and/or later use. Energy storage 120 may be implemented with battery cells 121 which will be managed for optimal performance. To use power from the energy storage 120, present invention implements a wireless power discharge channel, comprised transmitter and receiver pair 123. The wireless power charger channel 124 and wireless power discharge channel 123 is managed by electronics 106, which may be installed on the top of the charger stick and be combined with additional electronics to control the energy harvester, which may be implemented as a Photo Voltaic panel 140 which may be comprised of one or more Photovoltaic cells 141. A water tight component 142 can at least connect the energy harvester of arbitrary size and type to the control electronics 106 in said stick 100. In case of a photo voltaic energy harvester or windmill generator, the component 142 may contain a direction device to align the energy harvester to the energy source, for example to direct the photovoltaic cells towards the sun. We now turn to the components that are typical to the installation of present embodiment. The protective overhead structure, which may for example be a roof, comprised of one or more layers, such as for example but not limited to a op coating 112 and structural beams or insulation 113 will provide an opening with a diameter larger enough to receive a guiding interface 130. On said roof a watertight sealant 111 is installed to align around the opening and guiding interface 130 is installed in the opening, providing a water tight seal between the opening and the protective top cover 112. The guiding interface can be integrated with the sealant 111. Additionally, a protective construction 105 can prevent water entering the narrow air space between the stick 100 and the guiding interface 130. To secure the stick in the correct position, a ring 131 may be installed around stick 100. This will ensure proper alignment of the transmitter and receiver coils of the wireless power channels as well as provide theft prevention against malicious people on the roof after installation.

Installation of the stick through the protective overhead structure is shown in FIG. 12A. The present embodiment requires an opening in a roof (which may be drilled through a roof, or may be present from using pre-fabricated roof components such as e.g. plates with sufficient and suitable holes or other means). To install present invention, the following method is proposed:

1. Put a watertight sealant 111 around the opening (this may be a ring or paste or other material installed on the top of the roof).

2. Install a guiding interface 130 through the opening in the roof (which is installed preferably from the top of the roof, but may alternatively be installed from the underside of the roof).

3. Assemble the energy harvester (e.g. a Photo Voltaic cell or panel) to the charger stick.

4. Assemble the electrical load (e.g. a lamp) to the charger stick

5. Put the assembled stick through said guiding interface (preferably from the top of the roof)

6. The energy harvester may be optimally aligned with the ambient energy source.

7. optionally, a battery ring is installed over the stick. This enables to operate the load even when the energy source harvested by said harvester is not available. This step can be performed by moving the battery ring, which has an opening such as e.g. a round or otherwise geometric opening in the centre, over the stick until it slides in position. As a last step the stick is fixed from the inside (to protect against theft by a person walking on the roof and retracting the stick from the opening.

It shall be understood that:

-   -   Another sequence of the steps described previously is possible         and not excluded.     -   Instead of a roof a deck of a ship could be meant or another         surface, flat or curved, separating the outside of a space from         the inside of a space, eg a wall.     -   Instead of a building a hall without side walls could be meant,         or other building structures, that all share the requirement         that the space under the protective overhead structure may need         additional light at certain moments.     -   The stick 100, the central opening in energy storage 120 and the         central opening in guiding interface 111 or the holes in box 132         with top cover 133 will align perfectly, and the openings can be         shaped like prism or a cylinder, centred around a revolution         axis, wherein the central opening is centred around the         revolution axis.     -   The electrical load can be a light or other electrical load,         such as e.g. a radio or mobile phone connected via for example a         cable.     -   If the light guide is implemented, the device will provide light         during day and during night, but during the night the light will         come from the lamps powered from the energy storage whereas         during the day the light guide may provide all or part of the         lighting.

It shall be understood that another sequence of the steps described in FIG. 12A is possible and not excluded. A different sequence of installation steps is shown in FIG. 12B. In this sequence, the wireless stick is first installed (steps 1-3).

Once the wireless stick is installed, a battery ring can be fixed at step 4, and a luminaire can be attached to the bottom end of the stick at step 5. Eventually, the energy harvester is attached on top of the wireless stick at step 6.

In many cases it will increase the lifetime of the battery when it is installed on the underside of the protective overhead structure (e.g. the roof), since batteries tend to increase life if they are not operated outside. An example is Li-Ion batteries, which do not operate well under negative temperatures, and having the battery inside, in ambient temperatures, may offer an additional benefit. For example, in this case the outer insulation layer around the battery pack as described in the previous embodiments may be omitted depending on the installation conditions.

However, in case the battery is installed outside, the insulation layer can be useful to guarantee that the internal temperature of the battery stays within the comfort zone and in particular above a predetermined critical temperature.

In some cases it may be possible to use an alternative embodiment, which installs the battery from the top from the ceiling: This alternative embodiment is shown in FIG. 13. This variant will now be described in view of the differences to the other example described in FIG. 11

A box 132 is placed in the opening in the overhead protective structure. The box 132 can hold an energy storage module 120. A protective top cover 133 fits onto the box 132 and provides a water tight seal. Some protrusions or other guidance means align the centre opening in energy storage module 120 with the holes in the top cover 133 and box 132. The stick will be able to slide completely through said holes, so the installation can be completed wholly from the top of the overhead protective structure. The method to install the stick through the protective overhead structure and alternative embodiment from FIG. 13 is shown in FIG. 14.

As can be shown on FIG. 14, the method comprises the steps of

-   -   1) installing the sealant around the opening     -   2) placing the box 132 in the opening     -   3) inserting the battery ring 120 and closing the box 132 with a         top cover 133. The top cover 133 can comprise an opening in         which the wireless stick can be inserted.     -   At steps 4 and 5, the wireless stick can be assembled to         comprise the load and the harvester.     -   At step 6, the wireless stick is inserted through the top cover,         the battery ring and the bottom wall of the box 132.     -   At step 7, the wireless stick is fixed in position.

As described, this embodiment can be applied to through roof lighting system, lighting installations for small spaces, remotely located from main buildings, such as for example but not limited to car garages or car ports, garden cabbages, dachas or the like. This embodiment can be used for also lighting installations for single stock buildings, such as for example ware houses, etc.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiment with the lamps or luminaries as load devices. It can be implemented in connection with any type loads and any type of energy harvesters. Similarly, although the examples of this invention applies to Lithium-Ion based battery, it can be applied to other technologies of rechargeable batteries, like Ni—Cd batteries, Ni-MH batteries.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention may be practiced in many ways, and is therefore not limited to the embodiments disclosed. It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated. 

1. A battery module comprising an outer wall surrounding the battery module made of a thermally insulating material, a battery holder disposed within the outer wall comprising a plurality of battery receptacles in which batteries fit, and made of a thermally conductive material, a central opening, and a heat source disposed in the central opening of the battery module, wherein the heat source is a wireless power exchanger, comprising a wireless power tube coupled to the battery holder and disposed in the central opening, the wireless power tube being arranged for exchanging energy wirelessly with a wireless power stick that can be inserted into the wireless tube.
 2. The battery module of claim 1, wherein the wireless power tube comprises a winding for receiving power from the wireless power stick and for transmitting power to the wireless power stick.
 3. The battery module of claim 1, wherein the wireless power tube comprises a first winding for receiving power from the wireless power stick and a second winding for transmitting power to the wireless power stick.
 4. The battery module of claim 1, comprising a temperature sensor for sensing the temperature of the batteries in the battery holder.
 5. The battery module of claim 4, further comprising a controller arranged for monitoring the temperature sensed by the temperature sensor and for causing the heat source to be activated based on the sensed temperature.
 6. The battery module of claim 1, wherein the battery module is shaped like prism or a cylinder, centered around a revolution axis, wherein the central opening is centered around the revolution axis.
 7. The battery module of claim 6, further comprising a battery controller, said battery controller extending radially from the revolution axis between the central opening and the outer wall, occupying an arc segment of the base section of the battery holder, the plurality of battery receptacles being spread in a remaining arc segment of the base section of the battery holder.
 8. The battery module of claim 1, being shaped so that a plurality of battery modules can be stacked around a wireless power stick.
 9. A battery pack comprising a battery module of claim 1 and a wireless power exchanger for exchanging power with a load.
 10. A battery pack comprising a plurality of battery modules of claim 8, wherein the plurality of battery modules comprise each a central opening, the battery pack further comprising a wireless power exchanger formed by a plurality of wireless power tubes being each respectively coupled to the battery holder of each battery module of the plurality of battery modules and disposed in their respective central opening, and a wireless power stick inserted into the wireless power tubes of the battery modules and arranged for exchanging energy wirelessly with the plurality of wireless power tubes.
 11. The battery pack of claim 9, further comprising a power channel controller which is adapted to control the energy transfer with the battery modules based on at least one of the following parameters: internal temperature of the respective battery modules, input voltage from an energy harvester, input current from an energy harvester, position of the respective battery module in the battery pack, state of charge of the respective battery module.
 12. The battery pack of claim 11, wherein the power channel controller is adapted to control the energy transfer to an operating point having a selected efficiency based on an amount of heat to be injected in the battery module.
 13. Lighting system comprising, an illumination unit, a battery module in accordance with claim 8 for supplying the illumination unit in power, an energy source for supplying the battery module or the battery pack in power. 